One of the most pressing issues in contemporary European societies is the need to promote integration and social inclusion in the context of rapidly increasing migration. A particular challenge confronting national governments is how to accommodate speakers of an ever-increasing number of languages within what in most cases are still perceived as monolingual indigenous populations. This has given rise to public debates in many countries on controversial policies imposing a requirement of competence in a 'national' language and culture as a condition for acquiring citizenship. However, these...